Peel onions. Cut a thin slice from the bottom and top of each one. Scoop out a 1-inch deep hole from the top of each onion. Place onions, top sides up in a 2 quart microwave-safe dish with a lid. Add 1 beef bouillon cube and 1/2 T. butter to hole in each onion; cover with lid. Microwave, covered, at high, 8-10 minutes, or until onion is tender. Yields 2 servings.